The present invention relates to a concealed fastening building finishing element system that enables concealed fastening of finishing elements such as trim components, fascia boards, frieze boards, belly band boards, and the like to an underlying structure and to the fixings used in these systems.
The invention is particularly useful with trim elements around window and door frame openings and at building corners and will be described hereinafter with reference to these applications. It will be appreciated, however, that the invention is not limited to these particular fields of use and can be used in connection with other building finishing elements where concealed fastening is desired, including but not limited to, band board features, fascia boards, soffits and the like.
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.
In one popular form of building structure, trim installations are applied around window or door frame openings and at internal or external corners of a building. The trim serves both an aesthetic purpose in adding a decorative feature to building envelopes and also adds an additional weatherproofing purpose in allowing for more complete weatherproofing of building envelope corners and openings.
Without trim at the external corners of the building, for example, cladding such as planks or panels are each necessarily cut, nailed in place, and sealed against weather effects individually. Traditionally, a favored method was to mitre cut the plank edges to form a joint line which requires a high skill level. However, any building movements tended to cause the mitre joints to open up which as well as being unsightly, exposed the edges and the underlying structure to the weather. Additionally, because primary framing members are traditionally located at the external corners of buildings, it is important for the long term durability of a building that corner treatments are both easy to install and provide improved weather resistance for protection of the structural elements of the building.
Again, without finishing trim at window and door openings, the surrounding cladding panels or planks are necessarily individually cut, fixed in place and weatherproofed to a sophisticated level.
Trim may also allow for simplified installation of cladding such as planks and panels. At corners, for example, the trim is fixed in place first and then the cladding planks are simply square cut and fixed so that the cut edges of the planks butt up against the sides edges of the trim. A sealing compound is also used between the side edges of the trim and the cut edges of the planks to provide additional weatherproofing, without the need to individually treat each plank.
Trim is typically installed by driving fasteners, such as nails or screws through each the surface of trim member and into the underlying structure. The head of the nail or screw is thus visible on the face of the trim. On a pre-finished trim piece, if a smooth surface appearance on the face of the trim is required, the nails must be installed flush with the surface of the trim and the nail heads touched up with paint. If the nails are overdriven below the surface of the trim, the resulting holes must be filled with a water-proof filling compound and/or touched up with paint. It will be appreciated that these additional steps are time consuming and add additional cost to the installation.
U.S. Pat. No. 7,028,436 describes a corner trim piece which includes a cementitious layer moulded on a rigid right-angle backing. The rigid backing reinforces the cementitious layer and overhangs along one longitudinal side of the trim to provide a nailing flange for fixing the sheathing product to an exterior surface of a building. Holes may also be provided through the cementitious layer to allow nailing through the integrated sheathing product. While the reinforcing provided by the backing member provides resistance to cracking of the cementitious layer, it is also likely to increase the overall weight and cost of the trim piece. Additionally, manufacture of the integrated product is likely to be more complex than the manufacture of a simple discrete trim piece suitable for nail or screw fixing, as described above. Furthermore, this sheathing product is likely to have limited installation flexibility, in particular relating to ease of positioning the product in situ due to the nailing flange extending along the entire length of the trim piece. Furthermore, the described trim piece is necessarily provided as a pre-fabricated product and can only be used on corners limiting the flexibility on window and door trim installation.
Similar issues arise with the installation of other standard building finishing elements such as fascia boards, band boards, soffits and the like, in that face fixing through the element complicates the finishing process by requiring touch up painting or the use of prefinished or capped fasteners or the like. This is particularly relevant when prefinished finishing elements are to be used.